package/libargtable2: update LIBARGTABLE2_VERSION

Update LIBARGTABLE2_VERSION to reflect what is used by
https://release-monitoring.org

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/libargtable2/libargtable2.mk

@@ -4,9 +4,11 @@
 #
 ################################################################################
 
-LIBARGTABLE2_VERSION = 13
-LIBARGTABLE2_SOURCE = argtable2-$(LIBARGTABLE2_VERSION).tar.gz
-LIBARGTABLE2_SITE = http://downloads.sourceforge.net/project/argtable/argtable/argtable-2.13
+LIBARGTABLE2_MAJOR_VERSION = 2
+LIBARGTABLE2_MINOR_VERSION = 13
+LIBARGTABLE2_VERSION = $(LIBARGTABLE2_MAJOR_VERSION).$(LIBARGTABLE2_MINOR_VERSION)
+LIBARGTABLE2_SOURCE = argtable2-$(LIBARGTABLE2_MINOR_VERSION).tar.gz
+LIBARGTABLE2_SITE = http://downloads.sourceforge.net/project/argtable/argtable/argtable-$(LIBARGTABLE2_VERSION)
 LIBARGTABLE2_INSTALL_STAGING = YES
 LIBARGTABLE2_CONF_OPTS = \
 	--disable-example \